1. Field of the Invention
The present invention relates generally to acoustic position measurement of the location of under-water objects such as submersible vehicles and more particularly concerns apparatus for the measurement of the position of a tethered submersible vessel with respect to a surface support ship.
2. Description of the Prior Art
Acoustic pulsed transponder communication systems have been successfully operated in the past in the under-water determination of the locations of objects with respect to reference stations. For example, under-water range information has been derived by generation of acoustic carrier pulses abroad a surface vessel, transponders replying with corresponding acoustic pulses of a carrier frequency spaced apart from that received. However, prior art systems often require a plurality of under-water transducers and their individual locations must be precisely determined by making time-consuming and otherwise expensive surveys to determine the horizontal separations of the transponders.